The silicon solar cell with vertical multi-junctions (MJV) connected in series, is studied under monochromatic illumination in frequency modulation, for different cases of doping rate of its base. The diffusion equation relating to the density of minority charge carriers in the base of the solar cell is solved, taking into account the dynamic coefficient of diffusion (D(ω,N_b)) related to the doping rate (Nb) and to the frequency (ω) of modulation, as well as recombination speeds (Sf) at the junction and (Sb) on the rear face. From the expression of the photocurrent density of the minority charge carriers, the expressions (S_b (H,D (ω,N_b))) of the dynamic rate of recombination of the minority charge carriers on the rear face of the base, are established . Their graphical representations as a function of the thickness (H) of the base, makes it possible to determine the optimum thickness (Hopt), for different doping rates, for different frequency zones. The optimum Optimization … Malick NDIAYE et al.